Myrmecological News 16 69-74 Vienna, January 2012 Worldwide spread of Emma's dacetine ant, Strumigenys emmae (Hymenoptera: For- micidae) James K. WETTERER Abstract Strumigenys emmae (EMERY, 1890) (Subfamily Myrmicinae, Tribe Dacetini) is a tiny predatory ant (total length ~ 1.7 mm) that feeds on minute soil arthropods. Strumigenys emmae has spread to many parts of the world through human commerce. However, because S. emmae workers are so small and slow moving, most people remain unaware of their presence. To examine the spread of S. emmae, I compiled specimen records from > 350 sites worldwide. I documented the earliest known S. emmae records for 64 geographic areas (countries, island groups, major Caribbean islands, and US states), including many areas for which I found no previously published records: Anguilla, Antigua, Aruba, Barbados, Barbuda, Bonaire, British Virgin Islands, Cape Verde, Cayman Islands, Comoro Islands, Grenada, Îles Éparses, Jamaica, Montserrat, Palau, St Kitts, St Lucia, Tobago, and Trinidad. Strumigenys emmae appears to be originally from the Australian region, where all its closest relatives are found. Strumi- genys emmae occurs primarily in tropical areas. Almost all subtropical records come from peninsular Florida, plus a few subtropical records from the Bahamas, Japan, and Australia. Strumigenys emmae is most commonly found in intact xeric and mesic forest, as well as in planted areas around buildings, but rarely occurs in moist habitats. There is little information available regarding any possible impact of S. emmae on the native mesofauna in its introduced range. Key words: Biogeography, biological invasion, exotic species, invasive species. Myrmecol. News 16: 69-74 (online 4 November 2011) ISSN 1994-4136 (print), ISSN 1997-3500 (online) Received 15 February 2011; revision received 3 April 2011; accepted 4 April 2011 Subject Editor: Herbert Zettel James K. Wetterer, Wilkes Honors College, Florida Atlantic University, 5353 Parkside Drive, Jupiter, FL 33458, USA. E-mail: [email protected] Introduction Numerous tramp ant species, spread by human commerce, Berlese extractions of leaf litter from 14 of the 15 is- have achieved broad cosmopolitan distributions. Several lands. tramp ant species have become major ecological, agricul- BOLTON (2000) recognized 872 dacetine species. Of tural, and / or household pests, e.g., Anoplolepis gracilipes these, only three have achieved broad distributions in both (SMITH, 1857), Linepithema humile (MAYR, 1868), Mono- the Old World and the New World: Strumigenys rogeri morium destructor (JERDON, 1851), Monomorium phara- (EMERY, 1890), Strumigenys membranifera EMERY, 1869, onis (LINNAEUS, 1758), Paratrechina longicornis (LATREIL- and Strumigenys emmae (EMERY, 1890). The workers of LE, 1802), Pheidole megacephala (FABRICIUS, 1793), So- these three species differ in size (S. rogeri = 2.3 - 2.8 mm lenopsis geminata (FABRICIUS, 1804), and Tapinoma mela- total length, S. membranifera = 1.9 - 2.1 mm, S. emmae = nocephalum (FABRICIUS, 1793) (WETTERER 2005, 2007, 1.5 - 1.9 mm). The mandibles are long and linear in S. 2008, 2009a, b, WETTERER & al. 2009). Other tramp ants, rogeri, triangular in S. membranifera, and sickle-shaped in though widespread, have remained inconspicuous, e.g., S. emmae (Figs. 1 - 4). WETTERER (2011, 2012) examined Monomorium floricola (JERDON, 1851), Tetramorium bi- the worldwide spread of S. rogeri and S. membranifera. carinatum (NYLANDER, 1846), and Tetramorium lanugi- Here, I take a closer look at the smallest of the three cosmo- nosum MAYR, 1870 (WETTERER 2009c, 2010a, b). Among politan dacetine ants, S. emmae. the most inconspicuous are the tramp dacetines (Subfamily EMERY (1890) named this species after Emma Forel, Myrmicinae, Tribe Dacetini). wife of the eminent Swiss myrmecologist Auguste-Henri Dacetines are predatory ants that generally feed on Forel. DEYRUP (1997) called Strumigenys emmae by the springtails (Collembola) and other tiny soil arthropods common name "Emma's bowed-jaw snap-trap ant", and (WILSON 1953). Dacetines are small, cryptically colored, DEYRUP & al. (2000) called S. emmae the "bow-jawed and slow moving, and they become motionless when dis- pygmy snapping ant." I have used a simpler common name, turbed. As a result, most people, including field biologists, "Emma's dacetine ant." remain unaware of their presence even in areas where they Taxonomy and geographic origin are common. For example, CARROLL (2009) surveyed 15 bayhead tree-islands in the Florida Everglades and did not EMERY (1890) described Epitritus emmae (= Strumigenys find any dacetines in visual searches, yet found them in emmae) from St Thomas, US Virgin Islands. Junior syno- Figs. 1 - 4: Strumigenys emmae. (1) Head of a worker from Santa Cruz Island, Galapagos; (2) lateral view of the same worker; (3) dorsal view of the same worker; (4) worker at Archbold Biological Station, Florida (1 - 3 by A. Nobile, courtesy antweb.org; 4 by A. Wild). nyms of S. emmae include Epitritus clypeatus SZABÓ, lections of Archbold Biological Station (ABS, identified by 1909 from New Guinea and Singapore, Epitritus clypea- M. Deyrup), the Museum of Comparative Zoology (MCZ, tus malesiana FOREL, 1913 from Sumatra, and Epitritus identified by S. Cover), and the Smithsonian Institution wheeleri DONISTHORPE, 1916 from Hawaii. (SI, identified by B. Bolton). In addition, I used on-line BROWN (1949) placed Strumigenys emmae in the new databases with collection information on specimens by the genus Quadristruma with one other species, Quadristruma Essig Museum of Entomology at the University of Cali- eurycera (EMERY, 1897) (= Strumigenys eurycera), known fornia, Berkeley (UCB), Antweb (www.antweb.org), and the only from New Guinea. BARONI-URBANI & DE ANDRADE Global Biodiversity Information Facility (www.gbif.org). (1994) made Quadristruma a junior synonym of Strumi- I received unpublished records from J. Delabie (Brazil) genys. BOLTON (2000) placed S. emmae in the "emmae- and J. Czekanski-Moir (Palau). Finally, I collected S. group" along with six newly described Strumigenys species emmae specimens on islands of the Pacific, Atlantic, and all known only from Australia and placed S. eurycera in West Indies. the "eurycera-group" along with three newly described spe- I obtained geo-coordinates for collection sites from cies known only from New Guinea and neighboring is- published references, specimen labels, maps, or geography lands. Based on the distribution of its closest relatives, BOL- web sites (e.g., earth.google.com, www.tageo.com, and TON (2000) concluded that S. emmae originated in the Aus- www. fallingrain.com). If a site record listed a geographic tralian region. region rather than a "point locale", and I had no other rec- ord for this region, I used the coordinates of the largest Materials and methods town within the region or, in the case of small islands and Using published and unpublished records, I documented natural areas, the center of the region. I did not map rec- the worldwide range of Strumigenys emmae. I obtained un- ords of Strumigenys emmae found in newly imported goods published site records from museum specimens in the col- or intercepted in transit by quarantine inspectors. Pub- 70 Tab. 1: Earliest known records for Strumigenys emmae Tab. 2: Earliest known records for Strumigenys emmae from the Indo-Pacific. Unpublished records include collec- from Africa, the Arabian Peninsula, and neighboring islands. tor, museum source, and site. + = no previously published CAS = California Academy of Sciences. Other abbrevia- records. MCZ = Museum of Comparative Zoology. tions as in Table 1. ≤ Earliest record ≤ Earliest record + Papua New ≤ 1897 (EMERY 1897) + Equatorial Guinea ≤ 1899 - 1900 (BOLTON 1983) + Guinea + Ghana ≤ 1969 (BOLTON 1973) + Singapore ≤ 1909 (SZABÓ 1909 as E. clypeatus) + Seychelle Islands ≤ 1975 (MÜHLENBERG & al. 1977) + Indonesia ≤ 1911 - 1912 (FOREL 1913 as E. clype- ≤ atus malesiana) + Madagascar ≤ 2000 (BOLTON 2000) + Hawaii ≤ 1916 (DONISTHORPE 1916 as E. wheeleri) + Mascarene Islands ≤ 2001 (BLARD & al. 2003) + Mariana Islands ≤ 1945 (BROWN 1949) + Yemen ≤ 2002 (COLLINGWOOD & VAN HARTEN ≤ 2005) + Philippines ≤ 1945 (J.W. Chapman, MCZ): Dumaguete + Ascension ≤ 2003 (WETTERER & al. 2007a) + Malaysia ≤ 1946 (BOLTON 1983) + Cape Verde ≤ 2003 (J.K. Wetterer, MCZ): Mindelo + FS Micronesia ≤ 1950 (CLOUSE 2007) + Îles Éparses ≤ 2007 (B.L. Fisher & al., CAS): Com- + Vanuatu ≤ 1955 (E.O. Wilson, MCZ): 8 km SW ≤ bani, Mayotte ≤ Luganville + Comoro Islands ≤ 2009 (B.L. Fisher & al., CAS): Mohéli + Samoa ≤ 1956 (WILSON & TAYLOR 1967) + Australia ≤ 1958 (Darlingtons, MCZ): Tozer Gap Results + Solomon Islands ≤ 1963 (BOLTON 2000) I compiled Strumigenys emmae specimen records from + Japan ≤ 1975 (M. Shindo, MCZ): Chichi-jima > 350 sites worldwide (Fig. 5). I documented the earliest known S. emmae records for 64 geographic areas (coun- + Tonga ≤ 1980 (DLUSSKY 1993) tries, island groups, major Caribbean islands, and US states; Tabs. 1 - 4), including many locales for which I found no + India ≤ 1983 (BOLTON 1983) previously published records: Anguilla, Antigua, Aruba, Barbados, Barbuda, Bonaire, British Virgin Islands, Cape + Taiwan ≤ 1987 (TERAYAMA & KUBOTA 1989) Verde, Cayman Islands, Comoro Islands, Grenada, Îles + Tuamotu Islands ≤ 1987 (PERRAULT 1993) Éparses, Jamaica, Montserrat, Palau, St Kitts, St Lucia, To- bago, and Trinidad. + Society Islands ≤ 1991 (L. Morrison, MCZ): Tiahura In the Pacific (1995), I collected Strumigenys emmae at just one site in Tonga,